Leftovers:  Would you be more willing to eat them if you knew if they were still good?  At my house, leftovers usually don't stay around that long, I like to enjoy the same dish two days in a row once in a while, especially pizza.  Packaging that alerts consumers to food which is starting to go bad is being developed.  The plastic will change color when the food is about to lose its freshness because it has broken or damaged packaging.  (If it has exceeded its "best before date" or has been poorly refrigerated.)

The plastic is being created to help improve food safety and cut unnecessary food waste.  If you have ever used the excuse "I have food poisoning" to stay home from work, this could cramp your style.